1. Field of the Invention
The present invention relates to detecting smear as a cause of slider failures in a process of manufacturing a magnetic head (such as an HDD thin film magnetic head). In particular, the present invention relates to a method of, and a device for, detecting smear of a magnetic head capable of detecting the existence of smear in a state where a slider having an integrated head main body portion is in a bar shape before being cut into individual pieces.
2. Related Background Art
One example of a slider (an example of a five-pad slider) that configures this type of HDD thin film magnetic head is shown in FIGS. 9A and 9B, and another example (an example of a four-pad slider) is shown in FIGS. 10A and 10B. FIG. 9A and FIG. 10A show stages where a slider SL with an integrated head main body portion 10 has a bar shape before being sectioned into individual pieces. This shape is called a slider bar 1 here for convenience.
FIG. 9A is a schematic diagram of a five-pad slider having five pads (conductor surfaces), and FIG. 9B is a model diagram that shows an expanded view of the head main body portion 10. Each of the sliders SL has an insulator portion 22 bonded to (integrated with) a conductor portion 21 (for example, AlTiC: Al2O3—TiC), and bottom surfaces of the sliders form ABS surfaces (head surfaces). The head main body portion 10 of FIG. 9B is provided in the insulator portion 22 so as to be exposed in the ABS surface. That is, inductives (writing head portions) 11 and an MR element (reading head portion) used as a magnetic sensing element are embedded in the head main body portion 10 so as to be exposed in the ABS surface. Periphery portions of the MR element 12, and of electrodes 13a and 13b that are provided to both ends of the MR element 12 are surrounded by the insulator portion 22, and are sandwiched by shields 14a and 14b. 
Five pads, an R+ pad, an R− pad, an S pad, a W+ pad, and a W− pad, are provided to a rear surface of the slider SL that is perpendicular to the ABS surface with the five-pad slider of FIG. 9A. One electrode of the MR element 12, the electrode 13a, is connected to the R+ pad of the rear surface of the slider that is perpendicular to the ABS surface, and the other electrode, the electrode 13b, is connected to the R− pad of the rear surface of the slider. Further, the shields 14a and 14b are connected to the S pad. The inductives 11 are connected to the W+ pad and the W− pad.
Furthermore, four pads, the R+ pad, the R− pad, the W+ pad, and the W− pad, are provided to a rear surface of the slider SL that is perpendicular to the ABS surface with the four-pad slider of FIG. 10A. The S pad is not provided. The shields 14a and 14b are therefore connected to the conductor portion 21, which is made from AlTiC or the like. Other structures are similar to those of FIG. 9A. Identical reference numerals are appended to identical or corresponding portions, and explanations of those portions are omitted.
Wear (smear) may develop in the shield portions, and short circuits or insulation failures may occur between the shields 14a and 14b and the electrodes 13a and 13b when polishing the ABS surfaces (head surfaces) in the slider bar 1 state during a process for manufacturing HDD thin film magnetic heads (FIG. 9B shows smear schematically). Failures of characteristics such as an increase in the amount of noise in the magnetic head occur owing to smear, and sliders that develop smear are not used. That is, the sliders become defective parts.
Standard resistance values and resistance values after smear has developed are shown in Table 1 below for the five-pad slider and the four-pad slider. Resistance values among the R+ pad, the R− pad, and the S pad, or among the R+ pad, the R− pad, and the conductor portion 21 are shown.
TABLE 1Standard resistance valuesFive-pad sliderBetween R+ padBetween R− padBetween R+and S padand S padpad and R padSmear not present∞∞50 ΩSmear present1 kΩ or less1 kΩ or less50 ΩFour-pad sliderBetween R+ padBetween R+ padand conductorand conductorBetween R+portionportionpad and R padSmear not present1.25 kΩ1.25 kΩ50 ΩSmear present  1 kΩ or less  1 kΩ or less50 Ω
Among known techniques relating to conventional HDD thin film magnetic heads, those disclosed in JP 2000-182219 A and JP 3272329 B make reference to smear. However, both techniques relate to head structures in which smear hardly develops, and neither techniques relates to a method of detecting smear.